By Kat Harrold
Photo By Jorg Breuning
Mulching season is upon us the air is ripe it's fragrance. While the good gardener may protect their garden from unwanted weeds with a coat of mulch this can actually kill the functionality of a green roof.
The fine organic matter produced from the decaying mulch creates a hotbed for weeds that take advantage of the added nutrients. These same fine particles also clog the filter fabric and drains which result and standing water and roof load issues.
To protect your green roof from unwanted plants there are two main things you can do. The first is if it is a sedum roof, don't irrigate unless extreme drought lasting more than a month. The dry conditions often fry the seeds before they get a chance to germinate. Use only a small amount of slow release fertilizer twice a year for the first 4 years. Poor soils with a low level of nutrients are ideal for sedums. Excessive fertilizer can actually be detrimental to sedum growth while simultaneously providing excellent conditions for weed growth.